Apparatus



June 7, 1949. J.'V. M N'ULTY 2,472,671

ELECTRICAL APPARATUS Filed March 15, 1945 IN VENT 0R.

ATTORNEY Patented June 7, 1949 John vaMeNultwBinghamton, N. Y.;assignnftt Bend dyiationgqonporation, New York,:N. Yi alcorporatiomofDelaware Ani lie'atwnMamh it, 1945; Serial No.-58 2-8 96? 1"0 (ilaiins'w(c1. sis-21 3') The-zinventiomrelatesr; to'j electrical: apparatus;- andmore particularly: tokreleetrical f;circuits z-andv" means .v adapted'.-f0rvuse' in producing s-ele :trical:- arcs or: sparks suchyasthosesrequired? at' the? spark plugs;- inrthe ignition systems; foi"inter-nail 5e combustion; engines onthedike? One; of the.objectstof:ttheepresent' .irivention' is to; provide arz-novel.condenser-rdischarge"type' of? electricalcircu-it foIr-producing'highivoltage electtrical sparks between spaoed:.:electrodes.-1

Another object of -thevinventionds to provide a novel ignition; circuit:for; lnternalf'combustion enf-z;ginesor-the-likewhereinrtheourrentds:distributed:totransformercoilsi-ajcljapentttoron mQiint-ed in the sparkplugsat-irelatively'alow vol-taeeaandzrela-i tively high ,frequencyri Afurther objectwis; tocproifideinovelameans for controlling the: timinga'or frequency; ore sucoesq-r sivev impulses, of: electrical.- energydirected: to: a:- series 4 of spark gaps; such: as ithersparkwpiugs iiran ignition sys-tem :of-- an :e ine-nor'; the elike.

Still another" obj ect'i;iS"'-tO;pIlOVidewa circuit of" the abovecharacter. wherein-the energy iSfS'uDe plied by a magnetmgeneratorwandwhereinamighr sparking rate is: attainable: aoross-aesparkgap;.oifia: series ofspark gaps.

A still further. object detoprovide novelvmea'ns inacondenserdischargeetsipemf electricalr; sinsuit for effecting; aperiodic rdi'scharge o'f the stonage condenser," sald-zmeans beinggeffl-cieiit'i andi 80' dependable-in: operation: for: a; longs. periodof Still: another object isetor provide a indvelielecetricaloirouit-whiohdsadapted foriusel-irntheignit tion system: offengines 3: and: is: so con'struetedi that" a" lowdistributi0n.v0l.tage-= may: be-zsaif'e'ly and effeotively usedetherebyireducingrth'ef'radio shielding: Problems: and: minimlzingelectricallosses and-failures under1alli operatingwonditionsl The-,aboveandfurther, obj eotsand novel 'ife 4o turesof the inventiomwvii-l iiiorefully appear" from the followingbdetailed descriptionwvlieriwtlriersa-rna' is: read in? connection. with the ae'eompanyingidrawing; It is .ztofpbeeexpresslytunderstood;' however, that:thedratvingrisfior therrpurposetoieillus 45 trationonly-2'- andf: is.not: intended, to 7: define the limits 0f; the 1 invention;-,z.reference- 1 for this 2 lat ter purpose ebei-ngz-had iprimarily ;to theappendede claims;

In the drawingythee single;- figiire is; azisclie '56 matio diagram'illustrating one form: of spark generatingor ignition circuitwhich'embodies-rtlie presenttinvention; A

In the: cironitzillustratedi in the; drawing, by: wayi-ofziexamplezonly; the?inventlonisishownias; 55'

being embodied inf azix ignition:: system? suitable: for use inintern'abcombustidm engine's; the alet-' trioal energyb'e'i-ng'igeneratedl.andcsupplietkby "a magneto type generator-randdlstributedsatirelaei tivel'y low: voltageaanjderelativeimhighfrequencye: An ignition: system embodyingzthe' inventionxwilh beoperable at :a'llflaititndesaattainable by-wmode" ern'aircraft'withia'gmlnimuineof: electrical-1"losses-1 and Withoutappreciable danger "of: electrical iaile" ures.-. By reasonoii-th'egilotv xiistributionvoltagese the radio shielding -difllou'ltlesl andxrequirem'entsz; will also be substantially -redueedfln?such;a-zs'ys tem. It will the-understood; discourse;thatsithee invention isnot" limitediito use iii? an'iignitiomsy'se tem'b'ut may be i usefullyemployed ini-thealaborae' t'ory or in ma-ny :otlierwapplficatidnsiwhere'eit xis? desired to producaaEsrlesfofsparksracrossispaced?electrodes.

In" the: form" shown; thewndvelizelectrical: c'iiouit comprehendedhytheifirsent -invention some: prises a magnetoegneratonr I '0? as alsource of? electrical" energy. Although thewgenerator may? be in the'iormiv ofz any-bot?many-v known types of: magnetos; the." partioiilartype-s illustratede comi-Z prises a rfour-poleimagneticvrotomIIEandtlZitWOF- pole stator l2; the polesiao'f whic-h areconnected: by acore on -.which 'i:.is'i:wouxid:'a transformei coil having a? prlmarywindinglv I31 and a; secondary; winding l 42 The construction of thesewindings? may be varied; as is'z'well understood in the arty: for:obtainlng w'ithin rather Wide limits any de-": sired voltage inthekoiifcuitiof the secondaryawindp-i 1 ing;

In a-mannerwelleunderstoodrinrthe artiprimarya: windings I 3has:theaoppositeiendsthereof conenected? to the points i or contacts of;a circuit'z breaker. l5? Fbrnormally urging said contajcts toward:closed-on engaged position; suitable rear silient' means .suchzaszaiispring; I 62 may. be: roe. vided, and suitable means s'uch as arotatable calm I 7 maybe employedfifor periodically IHOViI'IfiiSflid"?points toxopencor disengaged, position; I as illus' f trated; forinterrupting the 'flomof- -cii'rreiit'in "the? circuit containing. thepfimary winding [3. Alithouglr a "sex-called:compensated-F camaoommer-"cially used in* radialiitypeqengiries iS flilhlstlated ilz it :wi'llibeunderstoodzithatrthicam may berdt'sanyasuitable; shape ands as; wens-iunderstood. i ,r the I art; 'saidicamispreierabljdriven at 'a'ispeedrpros portional 'torth'e" speed-o magneto rotor: l it One}-side.ofitheiprimarycircui s:conneoted togroundai as at l8 and 1awcoiidenseii Seisaconhectdacross? the points- 0f circuit breakenl 5 t'o'reduce: s'pa'rkf-i in wbetween'saidpointsewhenthe 'Same'aaiemQVedK to'openepos-itidn-liy thecmi For the purpose to appear hereafter,secondary winding I4 is tapped at approximately the center thereof andconnected to ground, such as at l8. In effect, this divides secondarywinding I4 into two windings with respect to the primary winding l3. Asshown, the ends or high potential turns of secondary windings it areconnected to the input terminals of two halfwave rectifiers 2U, 20.These rectifiers may be provided in the form of gaseous tubes of thecold cathode point-to-plane type, i. e., of the type wherein one elementhas a large surface and the other has a relatively small surface. Ifdesired, a single full-wave rectifier of the same type, for example oneknown commercially as Raytheon No. CK1004, may be used in lieu of saidtwo halfwave rectifiers, as illustrated in my cc-pending applicationSerial No. 567,672. As rotor H of magneto I is rotated, alternatingcurrent is induced in primary winding l3 and the circuit which iincludes circuit breaker l5. When the primary circuit is interrupted bythe opening of the points or contacts of circuit breaker l5, theintervals being determined by cam I! and the opening usually occurringwhen the primary current is at about its maximum value, current at ahigher voltage is induced in the secondary winding Hi, successiveimpulses being of opposite polarity. With the parts connected in themanner described above, the generated impulses of one polarity in thesecondary circuit will flow through one of the rectifiers or by way ofone input terminal of a full-wave rectifier and impulses of the otherpolarity will flow through the other halfwave rectifier 20 or by way ofthe other input terminal of a full-wave rectifier so that the outputfrom the plate terminals of the rectifiers will be unipolar.

The output or plate terminals of the rectifiers 2|), 20 are connected toeach other and to one terminal of a storage condenser 2|, the otherterminal of which is connected to ground as at 22. It is acharacteristic of rectifiers of the type illustrated that current willflow therethrough in only one direction, that is, current will flow frompoint to plane but will not flow in the opposite direction. Accordingly,when the rectifiers are connected in the manner shown, the electricalimpulses passing therethrough from the generator will be effective tocharge condenser 2i but the latter will be unable to discharge backthrough the rectifiers or rectifier, as the case may be, through thecoil of the magneto or other source. It is another characteristic ofthese rectifiers that the same will not become conductive below apredetermined voltage which is known as the on-set voltage. For mostdesirable operation, therefore, the maximum voltage generated across thesecondary circuit of the magneto at the minimum operating speed thereofmust be at least as great as the on-set voltage of the rectifiers and ispreferably approximately 100 or more volts higher than the on-setvoltage in order to provide a margin or factor of safety. For example,if the on-set voltage of the rectifiers is approximately 500 volts, thevoltage across the secondary circuit of the magneto at minimum operatingspeed should preferably be about 600 volts or more. The voltage of thecharge storedon condenser 2| may be varied by varying the capacity ofsaid condenser. After'calculating on determining the energy supplied tothe condenser from the secondary circuit of the particular magne'toemployed, it is possible to choose a condenser with a suitable capacityfor obtaining the desired voltage across the condenser. Thesecalculations may be made by the use of simple well known electricalformulas.

Novel means are comprehended by the present invention for controllingand timing the successive discharges of storage condenser 2| for thepurpose of creating periodic timed sparks across a gap or a. series ofgaps, said means being of such a nature that the elements thereof willhave a long operating life and at the same time permit a high sparkingrate. In the form shown, said means comprises a cold cathode gaseousdischarge tube 23 which may be of the type known commercially as astrobotron connected between condenser 2| and the load or work portionof the circuit to be hereinafter described. The high potential side ofcondenser 2| is connected to the plate or anode 24' of tube 23 and thecathode 25 thereof is connected to the load through a lead 29. A grid 26is provided between plate 24 and cathode 25 of the tube 23, said gridbeing normally maintained at ground potential or at some minimumpotential to act as a block to the passage of electrical current fromthe anode to the cathode. In the circuit shown, grid 26 is permanentlyconnected to ground, as at 21, through a suitable resistance 28, thefunction of which will appear hereinafter. Normally, therefore, tube 23is non-conductive and prevents the discharge of condenser 2|.

For the purpose of rendering tube 23 conductive to permit thedischarging of condenser 2|. novel means are provided for periodicallycreating a potential between grid 26 and cathode 25. Said means in theform shown comprise a condenser 30, one terminal of which is connectedto ground as at 27 and a resistance 3| which is connected between theother terminal of said condenser and the supply line from the source ofelectrical energy. Condenser 3G and resistance 3| are thus connected inseries with each other and in parallel with condenser 2!. Any suitablemeans such as a contactor 32 may be provided for periodically connectingthe high potential terminal of condenser 30 to grid 26 at a pointbetween the latter and resistance 28 in order to excite or trigger thetube 23, i. e., to render the tube conductive for the discharge ofcondenser 2|. As illustrated contactor 32 is constructed in the samemanner as circuit breaker I5 and the same is operated by a spring 33 anda rotatable cam 34, the latter being driven by the engine at a speedproportional to the speed of the engine crankshaft and, henceproportional to the speeds of rotation of rotor II and cam When theabove described circuit is employed for supplying electrical energy tothe spark plugs of a multi-cylinder internal combustion engine, theoutput terminal or cathode 25 of tube 23 may be connected through lead29 to the rotatable element 35 of an ignition distributor 36. As is wellunderstood in th art, element or arm 35 carries an electrode or brushwhich moves into successive conductive relationship with a series ofcircumferentially arranged terminals 31. In one suitable type ofdistributor, the rotatable arm 35 carries a carbon brush adapted toyieldably and successively engage contacts or terminals 31. Each of thelatter is connected to the primary winding 38 of a, high frequencystep-up transformer coil 38, the secondary winding 0 of which isconnected across the electrodes of a spark gap 4| such as the electrodesof a spark plug. One end of each of the windings 38 and 40 and oneterminal of spark gap 4| are connected Ii desired, the coils 39 may behoused within the radio shielding casing of the spark plugs. Sincesuitable distributors, coils and spark plugs are known and do not, perse, constitute a part of the present invention, it is believed to beunnecessary to illustrate and describe the same in more detail.

In the operation of the illustrated system,

'upon rotation of magnetic rotor I I alternating electrical currentimpulses are generated in primary winding I3, in a manner well known andunderstood in'the art, when the contacts of circuit breaker I5 are inclosed or engaged position. The circuit breaker I5 is periodicallyopened by cam II, preferably each time the current flow in winding I3approaches a maximum, thereby breaking the primary circuit and causing acurrent to be induced in secondary winding Hi. This alternatingsecondary current at a somewhat higher voltage is fed through therectifiers 20, in the manner fully described above for building upsuccessive unidirectional or unipolar charges on condenser 2 I. It willbe clear that the energy "for building up the desired charge oncondenser 2| may be supplied by a direct current generator or othersuitable direct current source without the use of rectifiers, but thisis not suitable in all installations or applications since the voltagedeveloped by such a generator varies substantially with variations inthe speed of the rotor. Although the timing of the operation of circuitbreaker I5 is not critical, it will be understood that for best resultsthe same should be properly coordinated in a known manner with the0peration of magneto rotor II and preferably the construction is suchthat the contacts of circuit breaker I5 will be separated just prior toeach closing of the points of contactor 32 which effects the propertiming of the sparks at gap 4 I.

As will now be apparent from the drawing, the electrical energy from thesource will be divided between the parallel connected branches of thecircuit which include condensers 2 I and 30. Thus, both of thesecondensers will be charged simultaneously upon each opening of circuitbreaker I5, at which times the points of contactor 32 will be in openposition. The presence of resistance to the flow of current from anode24 to cathode 25 and, hence, permit the discharging of condenser 2i. Theresistance 28 is inserted in the ground connection for grid 26 in orderto allow a potential'to be built up between the grid and cathode 25 whenthe contactor 32 closes. The connection through resistance 28 also tiesthe f grid 26 down electrostatically as hertoiore pointed out andstabilizes the gap between anode 24 and I cathode 25, thereby insuringagainst any discharging of condenser 2I before the -closing of contactor32. Accordingly, upon closure of contactor or circuit maker 32, thecharge on condenser 2I is discharged through tube 23 and distributor 35to the primary winding 38 of one of the coils 39. As is known, thedischarge of condenser 2| is a high frequency or oscillating dischargeso that a similar high frequency current is induced in secondary winding40 of the coil 39 at a considerably higher voltage, the step-up involtage being determined by the construction of coil 39. A spark andusually a shower or series of sparks are thus created across gap 4|. Theforegoing cycle of operation may be repeated at high speed for producingperiodic sparks across gap 4| or across a series of gaps connected inthe same manner with terminals 3'! of the distributor.

In one suitable embodiment of the invention in the form illustrated inthe drawing and heretofore specifically described, a standard magnetogenerator of the type currently used on modern aircraft engines wasemployed, the same being adapted to generate a'voltage of from 2-50 to300 volts across the primary circuit thereof. This voltage was steppedup to about 600 volts in the secondary circuit of the magneto whenrectifiers having an on-set voltage of approximately 500 volts wereused. Condenser 2I had a capacity of approximately .5 microfarad so thatthe voltage across the same when charged was approximately 350 volts.Resistor 3I "had a resistance of approximately 100,000 ohms and thecapacity of condenser 30 was only .005 microfarad so that the voltageacross the same when charged was approximately volts. The current flowthrough contactor 32 was on the order of a milliampere, therebyeliminating detrimental sparking at and consequent deterioration of thecontactor points. This also eliminates the erratic timing which isnormally experienced with contactors which are required to carry largecurrents at high voltages. The resistor 28 may have a resistance on theorder of 500,000 ohms. It will be understood, of-course, that theforegoing examples are illustrative only and that the electrical valuesof the various elements of the circuit may be varied between rather widelimits.

There is 'thus provided a novel electrical circuit and novel controlmeans therefor for producing electrical sparks which circuit, by way ofexample but not by way of limitation, is

' adapted for use in the ignition systems of internal combustion enginesor the like. Said circuit embodies novel simplified means forcontrolling the discharge of a condenser and, hence, for timing theoccurrence of sparks at one or a plurality of spark gaps. The circuit orsystem comprehended is reliable and efiicient in operation at allaltitudes and permits the production of sparks at a high rate whileusing a single source of electrical energy and a single control means.Other attributes of said circuit are long life and low cost ofmanufacture, installation and upkeep.

Although only a single embodiment of the invention is schematicallyillustrated in the draw ings and described in detail in the foregoingspecification, it is to be expressly understood that the same is notlimited thereto. For example, other Well known types of circuit breakersmay be substituted for those illustrated and suitable sources ofelectrical energy other than that illustrated.

may be employed; If accurate timing is not essential the contactor 32may be eliminated. Various other changes may also be made, particularlyin the design and arrangement of the parts illustrated without departingfrom the spirit and scope of the invention, as will now be understood bythose skilled in the art. For a definition of the limits of theinvention, reference is had primarily to the appended claims. What isclaimed is: 1. In an ignition system or the like, a storage-.cond.enser, a. second condenser, means for charging said condensers,asparkgap, a normally nonconductive. electronic discharge deviceconnected .between saidstorage condenser and said gap, and meansincluding a periodically and mechanically operable circuit maker foropcrably connecting said second condenser tolsaid device rforrenderingsaiddevice conductive .tcthe discharge of said storagecondenser.

2. Spark, producing-apparatus comprising a storage condenser, a source.ofelectrical energy for charging; said. condenser, a second condenserconnectedtosaidsourcednparallel with saidstorage condenser,.a;.discharge :device having an .anode connected .to said. storagecondenser, a cathode and a grid, at sparkgap connected to said cathode,and mechanically controlled means for periodically connecting saidsecond condenser to said grid .-for rendering said device conductive tothe discharge of said storage condenser.

3. In apparatus of the-class described, a storage condenser, meansfor-charging said condenser to a, predetermined voltage, a spark gap, adischarge device connected betweensaid condenser and said gap, saiddevice being .normally non-conductive at said voltage, .andmeansincluding a contact maker .and a second condenser, connected with saidcharging .means for periodically rendering said devicesuflicientlyconductive to permit said firstenamedcondenser itodischarge through saiddevice.

4. In apparatus :of thdclass described, a first condenser; a secondcondenser and a resistance connected in series witheach other and inparallel with said first'condensenan electronic discharge device havingan element-connected to said first condenser and being normallynon-conductive to a charge thereon, mechanically Operated means forperiodicallyconnecting another element of said device to said secondcondenser to thereby render. said 1 device capable of conducting thedischarge of said first condenser.

5. In apparatus of the class described, a first and a second condenserconnected in parallel branches of a circuit, an electronic dischargedevice having an anode; a cathode and a grid,

means connecting said first condenser to said anode, meanspermanentlyconnecting said grid to a point of low potential such as toground through a resistance, and means for periodically connecting saidgrid to the high potential side of said second condenserto render saiddevice conductive to the discharge of said first condenser.

6. In apparatus of theclass described, a source of unidirectionalelectrical current,circuit means connected to said source includingthree branches connected in parallel with each other, one of saidbranches including a condenser adapted to be charged by saidsource,;another of said branches including acondenser and a resistanceconnected between said second-namedcondenser and said source, another ofsaid branches including an electronic discharge device having the anodethereof connected to said first-named condenser, means for connectingtheagrid of said device to the high potential side ,of' saidsecond-named condenser, means for periodically opening and closing saidlast-named-connecting means, means including a resistance forpermanently connecting said grid to a poit of low potential such asground, and a spark gap adapted tobe connected to the cathode of saiddevice.

7. In apparatus of the class described, a con- ,.denser,. a, sourcecfunidirectional current; forcharging saidcondenser, a transformer,normally non-conductive electronic-means connected between saidcondenserand .said transformer, and means including .a second condenser connectedwith said source and mechanically controlled means for periodically.connecting said second condenser withsaid electronic means for rendering the latter conductive to permit said first condenser to dischargeacross .saidtransformer.

8. Inapparatus of the class described, a source of alternating current,means for rectifying the same, condenser means supplied from saidrectifying means,..electronic ,valve means connected to the output ofsaid condenser means, an induction coil also connected to the :condensermeans and the valve means-whereby the latter controls the energizationof, the coil from said source, and means for periodically triggeringsaid valve means including a second condenser means and a mechanicallyoperable timing means for periodically connecting said second condensermeans to the control element of said .valve means for rendering thelatter conductive .to the charge on said firstnamed condenser ,means.

9. In apparatusof the. class described, a source of electrical energy,condenser means chargeable .by said source, electrical valve -means and.an

energy-consumingload, such as the primary and across said load, saidtriggering means comprising a condenserchargeable by said source and acam operated circuit maker for periodically connecting the highpotential side of said condenser to the control element of-said valvemeans ,to render the latter conductive to the charge on said condensermeans.

10. In apparatus of the class described, a source of electrical energy,condenser means chargeable by said source, electrical valve means and anenergy-consuming-load, such as the primary winding .of a transformer,connected in circuit with said condenser means, and means forperiodically triggering said valve means to permit said condenser meansto discharge therethrough and across said load, said triggering meanscomprising a condenser chargeable by said source, means including acontact maker for periodically connecting the high potential side ofsaid condenser to e the control element of said valve means to renderthe latterconductive to the charge on said condenser means, and meansincluding a resistor for permanently connecting said control element topotential, such as to ground.

JOHN- V. McNULTY.

a point of low:

" REFERENCES CITED The following reterences are of record in the file ofthis patent:

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